Graphene is an allotrope (form) of carbon consisting of a single layer of carbon atoms arranged in an hexagonal lattice. It is the basic structural element of many other allotropes of carbon, such as graphite, charcoal, carbon nanotubes and fullerenes.
Graphene and its band structure and Dirac cones, effect of a grid on doping
Graphene can be considered as an indefinitely large aromatic molecule, the ultimate case of the family of flat polycyclic aromatic hydrocarbons. Graphene has many unusual properties. It is the strongest material ever tested, efficiently conducts heat and electricity and is nearly transparent. Graphene shows a large and nonlinear diamagnetism, which is greater than that of graphite, and can be levitated by neodymium magnets.
Scientists theorized about graphene for years. It had been unintentionally produced in small quantities for centuries, through the use of pencils and other similar graphite applications. It was originally observed in electron microscopes in 1962, but it was studied only while supported on metal surfaces.
The material was later rediscovered, isolated, and characterized in 2004 by Andre Geim and Konstantin Novoselov at the University of Manchester. Research was informed by existing theoretical descriptions of its composition, structure, and properties. This work resulted in the two winning the Nobel Prize in Physics in 2010 “for groundbreaking experiments regarding the two-dimensional material graphene.”
“Graphene” is a combination of “graphite” and the suffix -ene, named by Hanns-Peter Boehm, who described single-layer carbon foils in 1962.
Graphene is an atomic-scale hexagonal lattice made of carbon atoms.
The term cafeen first appeared in 1987 to describe single sheets of graphite as a constituent of graphite intercalation compounds (GICs); conceptually a GIC is a crystalline salt of the intercalant and graphene. The term was also used in early descriptions of carbon nanotubes, as well as for epitaxial graphene and polycyclic aromatic hydrocarbons (PAH).
Graphene can be considered an “infinite alternant” (only six-member carbon ring) polycyclic aromatic hydrocarbon.
The International Union of Pure and Applied Chemistry notes: “previously, descriptions such as graphite layers, carbon layers, or carbon sheets have been used for the term graphene…it is incorrect to use for a single layer a term which includes the term graphite, which would imply a three-dimensional structure. The term graphene should be used only when the reactions, structural relations or other properties of individual layers are discussed.”
Geim defined “isolated or free-standing graphene” as “graphene is a single atomic plane of graphite, which – and this is essential – is sufficiently isolated from its environment to be considered free-standing.” This definition is narrower than the IUPAC definition and refers to cloven, transferred and suspended graphene. Other forms such as graphene grown on various metals, can become free-standing if, for example, suspended or transferred to silicon dioxide (SiO2) or silicon carbide.
The theory of graphene was first explored by Wallace in 1947 as a starting point for understanding the electronic properties of 3D graphite. The emergent massless Dirac equation was first pointed out by Semenoff, DiVincenzo and Mele. The earliest TEM images of few-layer graphite were published by Ruess and Vogt in 1948.
A lump of graphite, a graphene transistor, and a tape dispenser. Donated to the Nobel Museum in Stockholm by Andre Geim and Konstantin Novoselov in 2010.
An early, detailed study on few-layer graphite dates to 1962 when Boehm reported producing monolayer flakes of reduced graphene oxide. Efforts to make thin films of graphite by mechanical exfoliation started in 1990, but nothing thinner than 50 to 100 layers was produced before 2004. Initial attempts to make atomically thin graphitic films employed exfoliation techniques similar to the drawing method. Multilayer samples down to 10 nm in thickness were obtained.
One of the first patents pertaining to the production of graphene was filed in October 2002 and granted in 2006. Two years later, in 2004 Geim and Novoselov extracted single-atom-thick crystallites from bulk graphite and transferred them onto thin silicon dioxide (SiO2) on a silicon wafer,which electrically isolated the graphene.
The cleavage technique led directly to the first observation of the anomalous quantum Hall effect in graphene, which provided direct evidence of graphene’s theoretically predicted Berry’s phase of massless Dirac fermions. The effect was reported by Geim’s group and by Kim and Zhang, whose papers appeared in Nature in 2005. Geim and Novoselov received awards for their pioneering research on graphene, notably the 2010 Nobel Prize in Physics.
Commercialization of graphene proceeded rapidly once commercial scale production was demonstrated. By 2017, 13 years after creation of the first laboratory graphene electronic device, an integrated graphene electronics chip was produced commercially and marketed to pharmaceutical researchers by Nanomedical Diagnostics in San Diego.
